AL-31F turbofan engine
The AL-31F aircraft engine is a modular two-shaft turbofan engine consisting of the following main parts: a gas generator (comprising low- and high-pressure compressors and turbines), an annular combustor, an afterburner and a nozzle, an accessory gear box and a control system. The compressor portion includes a 4-stage low-pressure module (with adjustable air flow) and a 9-stage high-pressure module. The engine uses a two-stage (HP and LP) turbine with adjustable radial clearance due to thermal expansion. It employs an annular combustor and a supersonic variable-area nozzle. The AL-31FP version incorporates a thrust vectoring nozzle.
Modernization of the engine included the installation of a FADEC-type digital control system, which provides improved acceleration capability and efficiency (an analog hydro-mechanical system was used previously). The modular design of the engine, together with the original design solutions, ensures its easy operation and the replacement of damaged components and parts in the field. The engine provides a high stall margin and can be used over a wide range of flight altitudes and speeds, operates under deep air intake surge conditions, including in spin flight, and also provides a unique maneuverability of the aircraft (performance of the Tailslide, Cobra and other maneuvers).
The AL-31F is installed on the Su-27 fighters and its versions, Su-33 shipborne fighters, Su-30MKK, Su-30MK2 multirole two-seat fighters and Su-34 front-line bombers. The AL-31FN with a bottom-mounted accessory gear box is used to power single-engine fighters (Chinese J-10A fighters). The AL-31FP version with thrust vector control is installed on Su-30MKI-type aircraft.
Carter Palmer, Power Systems Specialist, Forecast International, predicted that the AL-31F engine, has had a successful career with the type; however, engine production will go into steady decline during the next 10 years due to reduced orders for aircraft and possible future competition from the Chinese market.
The development of the engine AL-31F was closely linked with the development and beginning of lot manufacture of the heavy fighter of the 4th generation Su-27. The resolution about the start of development of this airplane was endorced in the year 1971. Already on the 20th of March, a pilot of this airplane, marked as T-10-1 took off. Until the year 1982, 9 test planes had been built, equipped with engines of the previous generation, AL-21F-3.
Qualitatively new fighters engine of the new generation was developed by the Moscow plant Saturn. For the airplane Su-27, the engine AL-31F was suggested on the base of an analysis, which has been carried out by CIAM. The competitors to this engine were D-30F-9 and R-59F-300. According to the original plan, the state examination of the engine were supposed to end in 1982, lot manufacture was to be ensured by Ufa-based UMPO.
The procces of projecting the engine did not go smoothly. At first, it was assumed that to minimalize the risk of technical complications, it will be a traditional scheme by-pass turbojet engine with a mixed afterburner chamber, which was already tested on engines D-30F-6. This concept also counted on a compressor of a low pressure ratio and a two-stage high-pressure turbine and two-stage low-pressure turbine. Therefore in the year 1974, the first long and heavy AL-31F came into being. Stend tests showed that such a concept cannot fulfill standards imposed on it. Subsequently A.M.Lyulka together with P.O. Suchoi made a dangerous decision about the start of a new prospective engine with single-stage turbines and compressors with a high-pressure ratio.
The decision about redesigning the airplane and engine was even more risky because the american equivalents F-15 and F-16 were already operationally used when developing MiG-29 and Su-27. There had not been practical experience in developing the revolutionary engine until then. When designing, it was necessary to address a number of serious technical problems related to the aerodynamic properties of the compressor, combustion chamber characteristics and reliability and features of the gearbox. The high pressure turbine was not operational until 1984. With many new untested technical solutions, the engine had no chance to pass the finishing tests, which are kind of a rehearsal for the state tests. The main problem lied in imperfection of the turbine blades and in September 1984, the main designer of Saturn, BM Cepkin decides that this part of the engine will be completely revised. All these problems resulted in delayed development of the engine compared to the airplane. Therefore, the first T-10 flew even with the old engines AL-21F-3.
The Su-27 was supposed to be produced in large batches, more than 100 airplanes a year, the Ufa-based UMPO however was unable to ensure the adequate supply of powerplants. It was therefore decided to engage AL-31F the Moscow plant Salut. In the first stage Salut produced only some elements of the engine, then the work was divided between the two plants so that the Ufa-based UMPO had the responsibility of cold parts of the engine and Salut’s were hot parts, while the Ufa-based UMPO maintained a position of head of production in the project AL-31F. Production in Salut started in May 1984.
|Full afterburner thrust, kgf||12 500|
|Min specific fuel consumption, kg/(kgf·h)||0,67|
|Inlet diameter, mm||905|
|Dry weight, kg||1,520(+2%)|
Second, creation of completely new engines based on the accumulated scientific and technical reserve. Here, on the one hand, it is important to choose the dimension and basic parameters of the engine correctly, so that later on it can be used to create the widest possible range of engines. On the other hand, a universal engine (or gas generator) will lose in terms of technical characteristics to an engine specially designed for a particular application. Therefore, given the high cost of developing a new engine, it is necessary to accurately find the edge on which the most optimally combined highly contradictory requirements for the GTE being created.
Taking into account the limited capacity of the state to finance the industry, Federal State Unitary Enterprise MMPP Salyut developed a concept for upgrading the commercially available AL-31F engine. The modernization of the AL-31F has the goal of increasing the thrust-economic characteristics, reliability and resource by gradually introducing progressive design and design-technological solutions into the serial engine design. The main trends in the development of modern aviation (weighting of aircraft (LA), increasing the range and height of flight, maneuverability and at the same time reducing the cost of production and operation) corresponds to the use of a modernized engine based on a proven design and ensuring the implementation of the above tasks without discontinuing existing fleet.
The implementation of a complex of works (development, fine-tuning, serial supply, operation and repair) under a unified leadership allows solving the problems arising at each stage in the shortest possible time. Combining all the works at the enterprise under a single start — promising developments, fine-tuning, production, serial maintenance, maintenance and repair — make FSUE MMPP Salyut sole and fully responsible for the creation of a modernized engine. the existing technological services, whose role has also increased, was created by the design office of promising developments (CISP).
At present, the KBPR is staffed with qualified specialists and works fruitfully. The equipping of workplaces with modern computing facilities integrated into a single information network allows to carry out integrated computer-aided design using the latest modeling methods and calculations of the engine as a whole, its individual components and parts. Modern computer technologies are used to conduct thermal and strength calculations, calculations of gas dynamics and combustion, for three-dimensional modeling and the preparation of design documentation.
The problem of creating a scientific, technical and technological reserve in one enterprise with a high technological culture and certain financial capabilities can be solved at a much lower cost from the state. A negative example in this regard is the story of the creation of one of the engines of the 5th generation, which was not finished at the time due to the presence of these problems.
The modern engine is the most technically complex technical system. The design of the engine, technological processes, ensuring its efficiency and high economic efficiency of production, must comply with world-class requirements. Therefore, from the modern technologies on the "Salute" choose those that are the most rational from the technical and economic points of view. The control programs for such equipment are developed by the specialists of the enterprise and abroad. Along with the use of purchased programs, we are developing our own specialized processors for programming the processing of turbomachine parts. Production at the FSUE "MMPP" Salyut "is certified. The plant has the weight of the necessary Russian and international quality system certificates, as well as a license for the design of gas turbine engines. We intend to achieve a consistent improvement of the basic engine parameters through three stages of modernization. Before each of them a certain amount is realized experimental design and engineering work, as well as a list of critical technologies that ensure the introduction of upgraded units. aetsya that drives each phase of modernization will be mass-produced, interchangeable with each other on the aircraft and have improved performance but compared with the previous ones.
Improving performance with ensuring interchangeability is achieved at the first stage of modernization (engine AL-31F-M1) efficiency is set with increased air flow. The temperature of the gas T3 before the turbine is increased by 25 o, the admissibility of which is confirmed by the necessary thermal calculations of the turbine. The analog regulator of the engine is replaced by a digital one. A turbo starter with a 15-20% increased power and up to 3,500 m of altitude launch is used. At the same time, the engine increases by 800 kgf compared with 12,500 kgf of the base AL-31F. The engine of the first stage of modernization has successfully passed bench and flight tests. Production is being prepared for its introduction into the series.
At the second stage of modernization (engine AL-31F-M2) in addition to the previous ones, adds high-temperature upgraded TVD and TND turbines with blades for spatial profiling are used. For the AL-31F-M2, AL-31F-MZ engines, a foundry version of the working blade (RL) of the multi-path longitudinal-transverse cooling circuit with perforation of the input edge was developed. Here, the cooling air enters the area of the inlet edge, where it is partially blown onto the profile, and partially through the horizontal (transverse) channels is supplied to the area of the outlet edge, where it is ejected into the flow part. This design allows XL to obtain a uniformly heated feather blades with minimal temperature stresses. The temperature of the gases increases by 75o
A newly developed prospective combustion chamber (CS) with a double-walled flame tube is used. This ensures the organization of combustion with high combustion efficiency, reliable start-up of the CS without the use of oxygen, reduced circumferential non-uniformity of the temperature field at the outlet of the CS, and increased resource of the CS with a significant decrease in cooling air flow An electronic-digital ACS is installed with full responsibility and hydro-mechanical redundancy. Engine thrust increases to 14100 kgf.
At the third stage of modernization (the AL-31F-MZ engine), a new three-stage CPR is additionally installed with wide-chord blades of spatial profiling and a higher compression ratio to p k = 4.2, which allows increasing the thrust to 14,600 kgf. At any stage of modernization, an all-round rotary nozzle can be installed on the engine, which is currently undergoing long-term tests. The implementation of the three stages will allow the creation of an engine with the characteristics of generation 4+. The new design and technological solutions tested during the modernization process can be taken as a basis for the development of promising engines for their further development.
Public Joint Stock Company (PJSC) "UEC-UMPO" (part of the United Engine Corporation of Rostec) initiated the process of introducing technologies obtained during the development and production of civil industrial gas turbine drives AL-31ST into engines for military aircraft. TASS was informed about this by Dmitry Lobov, director of the AL-31ST program of PJSC "UEC-UMPO".
"If earlier there was a process of conversion of the AL-31F aircraft engine into the AL-31ST industrial drive, now we can talk about the conversion process. A number of technologies obtained and tested in the process of creating and producing civil power plants are used in combat aircraft engines. ", - Lobov informed 30 April 2021.
According to him, civilian power units - the serial AL-31ST and the promising AL-41ST - have a number of common parts and assemblies with aircraft gas turbine engines. "There are common technologies, we are producing engines at one production base," added Lobov. The AL-31ST ground-based gas turbine engine is in the most demanded power range (16 MW) and is intended for use as a drive in gas pumping units. The effective efficiency of the motor is 36.0%, which gives the product a competitive advantage over drives of the same power with lower efficiency. Reliability, environmental friendliness and efficiency of AL-31ST allow using it in promising projects of PJSC "Gazprom".
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